This invention relates to an improved shutoff mechanism for a torque responsive, fluid operated tool.
Torque producing power tools driven by fluid such as pneumatic power tools are used extensively to attach fasteners and for other operations requiring a rotary shaft output. Many such tools are equipped with a clutch mechanism responsive to the torque imparted by the tool on the fastener. When a specific torque is reached, the clutch mechanism automatically slips and terminates further tool output to the fastener. Other types of tools include torque responsive shutoff mechanisms which shut off the supply of fluid to the tool once a specific torque level has been reached. Shutoff mechanisms help eliminate breakage and wear incurred in clutch control mechanisms. However, the time lag between torque sensing and tool shutoff may result in overtorqueing of the fastener.
Thus, tools have been developed which simultaneously incorporate a clutch mechanism and a power fluid shutoff mechanism to overcome the problems associated with wear of clutches in pure clutch mechanisms and overtorqueing associated with fluid motor shutoff mechanisms. A prior art mechanism of this type is illustrated in DePagter, et al., U.S. Pat. No. 4,078,618, for a "Torque Controller Shutoff Mechanism" issued Mar. 14, 1978.
Numerous additional patents which teach mechanisms for tool shutoff or clutch release upon sensing of appropriate torque levels including the following:
______________________________________ Issue Reg. No. Inventor Title Date ______________________________________ 2,986,052 Eckman, Predetermined Torque 5/30/61 et al Responsive Hand Tool 3,275,116 Martin Air Powered Tool with 9/27/66 Overload Cutoff 3,288,258 Taylor Torque Releasing Clutch 11/29/66 Mechanism 3,289,715 De Groff, Automatic Shut-off Tool 12/6/66 et al 3,373,824 Whitehouse Fluid Operated Tool 3/19/68 3,400,633 Amtsberg, Ultra-Torque Nut Runner 9/10/68 et al with Motor Brake 3,407,883 Amtsberg, Pneumatic Nut-Runner 10/29/68 et al with a Differential Pressure Switch Control 3,442,177 Ulbing, et al Torque Control System 5/6/69 3,473,439 Bratt Torque Release Means 10/21/69 for Rotary Pneumatic Tools 3,498,389 Tibbott Automatic Throttle 3/3/70 Torque-Responsive Power Tool 3,505,928 Whitehouse System for Performing 4/14/70 Tool Operation and Sig- naling Completion Thereof 3,512,590 Tibbott Automatic Throttle 5/19/70 Torque-Responsive Power Tool 3,512,591 Kulman Control for Torque 5/19/70 Producing Tool 3,515,225 States Rotary Impact Tool 6/2/70 Having Torque Responsive Disengagement and Power Control 3,515,251 Clapp Torque Release and Shut- 6/2/70 off Device for Rotary Tools 3,593,830 Clapp, Automatic Throttle 7/20/71 et al Torque-Responsive Power Tool 3,596,542 Wallace Pneumatic Push-Start, 8/3/71 Torque Shut-Off Screw Driver 3,616,864 Sorensen, Torque-Controlled Motor 11/2/71 et al Shutoff for Power Tool 3,642,039 McGee Power Screwdriver 2/15/72 Re. Bangerter Torque Release and Shut- 1/16/73 27,550 off Mechanism for Pneumatic Tools 3,766,990 Eckman, Low Torque Automatic 10/23/73 et al Screwdriver 3,811,513 Wezel Portable Pneumatic Power 5/21/74 et al Tool 3,970,151 Workman, Jr. Torque Responsive Motor 7/20/76 Shutoff for Power Tool 4,049,104 Webb Power Operated Torque 9/20/77 Tool 4,071,092 Wallace Pneumatic Screwdriver 1/31/78 with Torque Responsive Shut-off 4,108,252 Stroezel Power Driver for 8/22/78 Threaded Fasteners 4,113,080 Thackston, Torque Wrench Air Shut- 9/12/78 et al Off 4,120,604 Garofalo Portable Pneumatic Nut 10/17/78 Running Tool Having Air Shut-Off Controls 4,154,308 Goldberry, Low Torque Automatic 5/15/79 et al Screwdriver 4,191,282 Schoeps Device for Tightening a 3/4/80 Screw Joint 4,223,745 Workman, Jr. Torque Responsive Motor 9/23/80 Shutoff Mechanism for Fluid Operated Tool ______________________________________
Of particular pertinence to the present invention are the teachings in U.S. Pat. Nos. 3,811,513; 3,593,830; 3,512,591; 3,512,590; and 3,289,715, as well as the DePagter et al patent referenced above. While each of the prior art references teaches a useful and utilitarian construction, an improved and simplified clutch mechanism and torque responsive shutoff mechanism which also is operative to initiate operation of the tool is desirable.